This invention relates generally to the field of optical imaging and more specifically to the field of optical image guided procedures.
There is a pressing need for new high-resolution (xcx9c10 xcexcm) imaging and visualization technology across a wide range of fields including medicine, medical and biological research, and materials and packaging research, development, and manufacturing. Improved visualization can enable new diagnostic capabilities such as in diagnostic screening of the esophagus for adenocarcinoma or in locating voids in multi-layer polymer packages. In addition, improved visualization enables new image guided procedures such as guiding an atherectomy catheter to remove small unstable plaques from a coronary artery without puncturing the arterial wall.
MRI, x-rays, ultrasound, and optics have all found important roles in imaging applications. In many applications optical imaging offers certain advantages over other approaches because it is non-ionizing, non-contact, and can achieve high resolution. There are a variety of types of optical imaging techniques concurrently available including optical coherence tomography (OCT) and other interferometric imaging techniques, fluorescence and other spectroscopic imaging techniques, Raman imaging, diffuse-wave optical imaging, and two-photon imaging techniques.
OCT is an interferometric imaging technology and thus has the properties of very high sensitivity and large dynamic range. OCT achieves depth resolution via a combination of the focal properties of the imaging optics used and the coherence properties of the optical source used. The use of OCT and other interferometric imaging modalities has three fundamental advantages over standard direct detection optical imaging techniques: 1) the ability to achieve nearly shot-noise-limited detection and thus high sensitivity ( greater than 140 dB), 2) the ability to achieve high dynamic range ( greater than 100 dB) as the received signal is proportional to the electric field, not the intensity as in direct detection, and 3) the ability to perform high-resolution phase-sensitive temporal gating yielding significantly improved depth discrimination (xcx9c1 xcexcm).
Most previous work on scanning methods used in probe modules that attach to OCT or other optical imaging systems have focused on utilizing galvanometric or stepper based transverse scanning to produce multi-dimensional images. For instance, U.S. Pat. Nos. 5,459,570 and 5,321,501 describe several OCT imaging embodiments and their application in ophthalmology. These patents include methods which scan a beam in transverse patterns on the retina or on the anterior eye using galvanometer controlled mirrors or rotating mirrors. For endoscopes and catheters, methods have been described which scan a beam in a circumferential transverse direction perpendicular to the longitudinal axis of the catheter or endoscope. For example U.S. Pat. Nos. 5,393,467, 5,459,570 and 5,321,501 describe forms of these techniques.
It is an object of this invention to provide a forward directing imaging system that is useful for diagnostic and therapeutic intervention during medical procedures. The imaging system described has application to hand-held probes, laparoscopes, endoscopes, catheters, guidewires, trocars, microscopes, tissue probes, needles, scissors, scalpels, and other instruments either as xe2x80x9cstand-alonexe2x80x9d implementation or as a new implementation used in conjunction within, or external to, an existing instrument.
In one embodiment, the present forward directing imaging system includes forward directed optical coherence tomography (OCT) in a probe including a scanning mechanism. In another embodiment the system uses non-retroreflected OCT and includes a light source, a sample illuminator, a reference arm, a beam splitter, a sample light collector, a detector to generate a signal in response to incident light, and a beam combiner positioned to direct light from a sample light collector and a reference arm to a detector where output from the detector is analyzed by a computer.
In another embodiment the optical probe imaging system includes a scanning mechanism capable of causing a lens and optical fiber to move substantially orthogonally to the longitudinal axis of the housing. In one embodiment, the scanning mechanism includes a motor and a cam attached to the motor. The motor causes rotation of the cam moving the lens and optical fiber to orthogonally to the longitudinal axis of the probe housing to scan a sample. Other embodiments of the scanning mechanism which cause the lens and fiber to move orthogonally to scan a sample include a piezoelectric transducer, or by a wire around a pivot, pneumatic devices, or by an electrostatically driven slide.
In another embodiment of the optical imaging system, the scanning mechanism includes counter rotating prisms or rotating offset lenses that generate arbitrary scanning patterns on a sample.
In another embodiment of the invention the forward scanning OCT imaging system may be applied in a hand-held probe, or surgical tools such as probes, scalpels, scissors, forceps and biopsy instruments. Embodiments of these devices include the application of surgical laser fibers.
In yet another embodiment, the optical probe is an endoscope used to examine natural orifices, canals, tubes, ducts and vessels of the body. The invention contemplates a surgical grinding endoscope which uses a cutting element in the forward or side direction combined with the forward imaging capabilities of the optical probe.
In another embodiment of this invention, the OCT imaging system is used with a laparoscope to perform diagnostics and surgical procedures within body cavities. The laparoscope embodiment also contemplates the use of forward scanning lasers.
In still another embodiment of the invention, the imaging system is applied to a surgical microscope for procedures requiring an en face as well as a cross sectional view into the tissue. The imaging system is also applied to a high numerical aperture microscope in yet another embodiment of the invention
Another important embodiment of the invention is for therapeutics such as atherectomy, transurethral prostatectomy, and cervical imaging. It is contemplated that the optical probes of this invention are implantable to allow for continuous or periodic extraction of information from the tissue site where implanted.